The spin cycle of a washing machine removes water centrifugally from wet clothes by spinning the clothes at high speed in a spin basket. In order to reduce the possibility of injury to the user during the spin cycle, it is known to use an electronically actuated lock for holding the washing machine lid in the closed position. U.S. Pat. Nos. 6,363,755; 5,823,017; and 5,520,424, assigned to the present assignee and hereby incorporated by reference, describe several locking mechanisms. Desirably, the locking mechanism minimizes projecting parts on the washing machine lid which might snag clothing or reduce access to the spin basket and is simply integrated into the washing machine housing.
A signal indicating the state of the washing machine lid as opened or closed may be used to ensure the lid is closed before the lock is engaged. Such a signal may be provided by a switch communicating with the washing machine lid. Ideally such a switch could not be easily defeated, would operate reliably when used with other washing machine components with normal manufacturing tolerances, and would be resistant to contamination by water and dirt.
U.S. Pat. No. 7,493,783, hereby incorporated by reference, describes a lid lock that can sense whether the lid is closed by distinguishing between an “over-travel” position of the lock bolt that can occur when the lock bolt is extended and the lid is up and so does not block the extension of the lock bolt, and an “engagement” position of the lock bolt that occurs when the lid is down and the lock bolt is received by the lid blocking overextension. A controller, by distinguishing between three electrical signals indicating, respectively, the unlock position, the over-travel position, and the lock position, can determine that the door is properly locked with the lid engaging the lock bolt.
U.S. provisional application 61/711,418 filed Oct. 9, 2012, and hereby incorporated by reference, describes a lock bolt actuator employing a mechanical element responding to successive pairs of forward followed by reverse actuation from a bidirectional electric actuator, such as a motor, to provide three distinct lock bolt positions (unlock, lock and over-travel position) depending on the presence or absence of the lid. The lock position is blocked against retracting when an external inward force is applied on the bolt. A unique signal indicating that the bolt is either in the engaged position or over-travel position combined with controller logic allows the appliance controller to determine if the lid is closed and locked with only one binary signal.